<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script type="text/javascript">
			var fun = function(){
				var btn = document.getElementById("btn");
				var text = btn.innerText
				text = "<b>"+text+"</b>"
				//btn.innerHTML = text
				btn.innerText = text
			}
		</script>
	</head>
	<body>
		<button onclick="fun()" type="button" id="btn">按钮</button>
	</body>
</html>
